Extensible trestle



Aug. 2, 1960 B. l.. BRYNJoLFvssoN EXTENSIBLE TRESTLE Filed June 29, 1959 2 Sheets-Sheet 1 INVENTOR 5LB/WAN o/ FSSON BY JK M- TTORNEY U- 2, 1960 B. l.. BRYNJoLFssoN 2,947,378

EXTENSIBLE TRESTLE 2 Sheets-Sheet 2 Filed June 29, 1959 2 24 M T- i 27 as INVENTOR HLRr/vuoLf-ssa/v United States Patent O M EXTENSIBLE TRESTLE Bergur L. Brynjolfsson, 4'520 N. Clifton Ave., Chicago, Ill.

Filed June 29, 1959, Ser. No. 823,609

4 Claims. (Cl. 182-10S) This invention relates to an extensible trestle or adjustable scaffold support and has for its primary object to provide a supporting unit which may be easily adjusted vertically, and including novel clamping units for adjustably clamping an extensible upper section of the trestle to the lower section thereof, and whereby the weight borne by said extensible upper section will urge the clamping units into tight clamping engagement with said upper section for rigidly positioning the upper section relative to the lower section of the trestle.

A further object of the invention is to provide an extensible trestle or scaffold support including clamping units for adjustably securing the extensible upper part of the trestle to the lower part thereof and through which the extensible upper part of the trestle may be readily Y moved vertically relative to fthe lower part of the trestle,

when no weight is supported thereby.

Various other objects and advantages of the invention will hereinafter become more fully apparent from the following description of the drawings, illustrating a presently preferred embodiment thereof, and wherein:

Figure 1 is a fragmentary side elevational view of the intermediate portion of the trestle;

Figure 2 is an enlarged fragmentary elevational view, partly broken away and partly in vertical section, looking toward the opposite sides of the trestle parts as seen in Figure l;

Figure 3 is a horizontal sectional view taken through the upper part of the base portion of the trestle, substantially along a plane as indicated by the line 3--3 of Figure 4;

Figure 4 is a fragmentary vertical sectional view taken substantially along a plane as indicated by the line 4--4 of Figure 3;

Figure 5 is a fragmentary transverse vertical sectional view, taken substantially along a plane as indicated by the line 5-5 of Figure 3;

Figure 6 is an enlarged fragmentary vertical sectional view, in detail, taken substantially along a plane as indicated by the line 6-6 of Figure l, and

Figure 7 is a fragmentary exploded side elevational view of certain of the parts of the extensible trestle.

Referring more speciically to the drawings, the extensible trestle or scaffold support, designated generally 9, includes a base section 10 and an extensible upper section 11. The base section 10 includes two corresponding legs 12 and 13, each of which is composed of a straight ladder having side rails 14 connected by spaced rungs 15. The two ladders or legs 12 and 13 are of the same length and preferably of the same construction. The extensible upper section 11 likewise is composed of a straight ladder having spaced side rails 16 connected by spaced rungs `17. The trestle parts 11, 12 and 13 are conventional and may be of any desired lengths. u

The extensible trestle 9 includes two corresponding connecting and clamping units, designated generally 18 and 19, for connecting the ladders or legs 12 and 13 of 2,947,378 Patented Aug. 2, 1960 ice the extensible upper section 11 to said base 10. As the connecting and clamping units `18 and 19 are identical in construction, a description of one will suffice for both.

Each unit 18 and 19 includes a pair of bracket arms 20 and 21 each having an outwardly turned back outer end portion forming an inwardly opening hook or channel 22 of a proper shape and size to fit snugly around three sides of a ladder rail 14. The portion 22 of the arm 20 engages around the upper portion of one of the rails 14 of the ladder or leg 12 and the portion 22 of the bracket arm 21 engages around the upper end of the complementary rail `14 ofthe other leg or ladder 13. Said portions 22 are secured rigidly to said rails 14 by fastenings 23. The bracket arms 20 and 21 extend inwardly from the inner sides and inner edges of said rails 14 and are disposed crosswise of the ladders 12 and 13 and have overlapping inner free ends 24 and 25, of the bracket arms 20 and 21, respectively, which are provided with registering openings 26. The shank of a bolt and nut fastening 27 extends outwardly through the openings 26 for pivotally connecting the bracket arms 20 and 21 together. It will thus be seen that the fastenings 27 of the two connecting and clamping units 18 and 19 pivotally connect the two ladders or legs 12 and '13 of the base 10 to one another at the upper end of said basel and that the axis of the base pivo-t 27 is disposed between the upper ends of the legs or ladders 12 and 13, as seen .in Figures l, 3 and 5.

Each clamping unit 18 and 19 includes two elongated channel shaped clamping elements 23 and 29 having complementary inner longitudinal edges 30. The clampthe base 10 to one another and for adjustably clamping y ing element 28 has an apertured ear 31 projecting from its inner edge 30 and the clamping element 29 has a similar apertured ear 32, also projecting from the edge 30 thereof. The ear 31 is outwardly offset slightly, as best seen in Figure 3, for overlying the outer side of the ear 32. The bolt of the fastening 27 of the clamping unit 18 or 19, of which said clamping elements 23 and Z9 form a part, extends outwardly through the aligned apertures of the overlapping ears 31 Vand 32 and thence through the openings 26, and the head of 4the bolt of said fastening bears against the inner side of the inner ear 32, for pivotally mounting the clamping elements 2S and 29 relative to one another and to the bracket arms 29 and 21. The longitudinal edges 30, which are disposed adjacent the arms 20 and 21, are spaced from one another, above and beneath the ears 31 and 32, when said clamping elements 28 and 29 are disposed substantially parallel to one another, as seen in Figure 5. The clamping elements 28 and 29 have opposite opposed longitudinal edges 33 and 34, respectively, which are likewise spaced from one another when said clamping elements are disposed parallel.

The clamping element 28 has an outwardly turned back extension 35 forming an integral continuation of a part of the edge 33 thereof and which is disposed substantially parallel to the bracket arms 20 and 21. A lever arm 36 is pivotally connected, near one end thereof, to the outer side of the extension 35 by a fastening 37. Said extension 35 and the fastening 37 are disposed substantially below the level of the fastenings 27, as seen in Figures l and 2. The clamping element 29 has an outwardly turned back folded extension of its longitudinal edge 34 and which forms an inwardly opening channel 38 which -is disposed at an incline relative to the edge 34, so that the upper end thereof is set back from the edge 34 while the lower end thereof protrudes slightly beyond said edge 34, as best `seen in Figure 2. Said channel 38 is also disposed near the lower end of the clamping element 29. The intermediate portion `of the upper edge of the lever arm 36 is provided with an arcuate notch 39,

bracket, arms 20 and 21 relativetotone another.

and the free end of said arm 36, which is disposed remote from the pivot 37, is inclined slightly as seen at 40 to conformably engage the bed of the channel member 38 .when the lever armr36 is disposed nearlyhorizontal `but inclined upwardly slightly, as seen in Figure 2, f-rornits `pivot 37Vtowardsaid end ,40.

upper edge of the endA 25 of the bracket arm 21.is provided with an elongated arcuatenotch 42 which is con .centrically disposed .relative tothe opening .26 of the bracket arm 21 andinto which the lug or tongue 41 projects. ,Said lug or tongue 41 is `slidably movable, in the notch 42 t0 allow a limitedA pivotal movement. of the When the legs or ladders 12 and 13 aredisposed substantially parallel to one anothenas seen in Figure 5, the lug 41 vengages one end of the notch 42 to prevent further swinging movement of the lower portions of said legs 12 and 13 toward one another. When thelegs or ladders 12 Vand 13 are fully extended so` as to extend downwardly .parallel positions relative to one another, 'as seen in `Figure 5, when the legs or ladders 12and y13 are spread to fully ope-n positions, as seen` in Figures l and 2. The side rails 16 of the upper extensible section 11 are spaced apart a distance less than the spacing between the side rails 14 of each of the ladders .12 and'13 and a distance so that one rail 16 can flt in the channels fof the clamping elements 28and 29 of the connecting vand clamping unit 18 when the other rail 16 is engaging in the channels of the clamping elements 28 and 29 of the unit 19. With the clamping elements l28 and 29 disposed -in substantially upright positions, the edges 33. and 34 of each pair of said clamping elements are disposed sufliciently far apart so that portions of the rungs 17 may pass therebetween. Accordingly, the extensible upper section 11 with its rails 16 engaging the pairs of clamping elements 28 and 29, as previously described, may be slid upwardly therethrough. As each rung.17 passes upwardly between the edges 33 and.34, portions of the rung will engage the bottom edges of the ,two lever arms 36 to cause the ends 40 thereof to swing upwardly to permit the run to pass said, lever arms.

. When the upper section 11 has been extendedto adesired height, the lever arms 36 can be swung downwardly toward the channels 38 or may swing toward said .channels by gravity until the lever arm ends 40 engage iii" the channels 38. The upper section 11 is then lowered .until portions of one of the rungs 17 thereof Will comev to rest in the notches 39. When this occurs, the weightof the upper section Y11 will force the lever arms 36 to swing downwardly toward their positions as` Aseen in Figures 1 and 2. In so moving, the ends 40 of the lever'armsby a camming engagement with thebeds ofthe lchannels 38 will'frce the lclamping elements .28 and29 to pivot about the fastenings 27 so that the'lower end s thereof will swing Vapart and the upperV yends 43 thereofwill be swung toward one another and into clamping engag. ment with the rails 16 above the rungs`17 vwhich :engages the notches 39. Engagement of the portions 43 with the rails 16 will prevent Athe loweriportio'ns of the clamping elements 28 and 29 from swinging further apart thanas shown in Figures l and 2, and in 'whichj'posrition the. vlever arm ends .40. are wedged in the channels-'38' and areprevented from swinging downwardly past 4the position .of the .lever arm 36 as seen in Figure 2. The weight of the upper trestle section 11 and the platform or other load supported thereby, not shown, will effectively maintain the pairs of clamping elements 28 and 29 in tight clamping engagement with the rails 16 and will also maintain one of the ladder rungs 17 securely seated in the notches 39 for supporting the upper section 11 rigidly with respect to the base 10.

'I'he clamping elements 28 and 29 have been illustrated of arcuate cross section to conformA to .the..circular or tubular shape of the vrails 16;"however, said elements 28 and 29 could be of other cross sectional shape to conformably e'rigage rails' of othercr'oss 'sectional shapes.

Various modifications and changes are contemplated and may be resorted to, without departing from the function or scope of the invention as hereinafter deiined by the appended claims.

I claim as my invention:

l.. An extensible trestle comprising,. in combination with a pair of ladders disposed in downwardly diverging relation to'one another and forming a trestle base and a ladder extending upwardly from the baseand forming an extensible upper section of the trestle; connecting` and clamping units hingedly connecting the upper ends -of the base 4ladders to'one another and adjustably supporting the extensible section ladder therebetween, each of longitudinal edge thereof and forming a lever arm,'fs'aid said units including a pair of bracket arms rigidly secured of `thetwo base ladders and having overlapping inner ends disposed'between said rails, al fastening extending loosely through said overlapping inner ends and pivotally connecting said rails of the two ladders toV one another betweenthe ladders, each of said units including a pair of elongated clamping elements of channelY shaped cross section having complementary longitudinal edgesv'provided withr overlapping extensions through whichsaid fastening loosely extends for pivotally mounting said clamping elements on inner sides ofthe bracket arms, said .fastenings being spaced from upper and lower ends of said clamping elements, the clamping elements-of said two units being disposed between the bracket armsvth'ereof,'the rails of the ladder of the extensible upper section fitting. slidably in said pairs ofclamping elements, the `otherrinner longitudinal edges of the clamping elements of each .pair being spaced apart a distance lsuflicient to 'permit the rungs of said upper extensible ladder to slide freely therebetween for extending or retracting said upper section vertically relative to the trestle base, andV means fovr..clo4s'ing` the gap between said inner edges of said .clamping elements, beneath the fastening thereof, to pro- -for rigidly supporting said extensible ladder relative to thetrestle base. l

2. An extensible trestle as in claim l, said closing means comprising a bar pivotally connected to the outer iside Vof 'one of the clamping elements near the inner other clamping' element having a rigid channel portion 'disposed on `the outer side thereof and opening ftoward the arm pivot, said channel portion being disposed atan incline downwardly toward said inner longitudinal`fedge last mentioned clamping element lto combinefwith the freerend `of the arm to form the cam 'means"and wherebvsaid Yfree end of the .arm is wedged in said Chan- .nel .portionagainst downward Swinging mOi/ement when the upper, ends .of the lClamping elements are swung ,-in- :wardlyinto clamping engagement with .the ladderirail.

SQAn extensible trestle as in claim'2, said arm having 0ftherung,` engaged bythe arm, seats, said notchconur operating with the upper ends of the clamping elements to retain the upper trestle section immovable relative to the trestle base.

4. An extensible trestle as in claim 1, and means interconnecting the bracket arms of each of the connecting and clamping units for limiting pivotal movement of said bracket arms relative to one another for limiting swinging movement of the ladders of the trestle base toward open extended positions.

References Cited in the le of this patent UNITED STATES PATENTS 

